[21-Feb-2024] Chen, Y., Menezes, V., Yu, L., Carrigg, J., Steele, M., and Zippel, S.
Presented at the 2024 Ocean Sciences MeetingIn recent decades, the open-water period during which the Arctic is sea ice-free is lengthening, leading to notable changes in air-sea heat, momentum, and water fluxes and associated biogeochemical processes. In this study, we examine several reanalysis data sets (ERA5, MERRA2, and CFSv2) and observations from a recent field campaign (NASA SASSIE cruise in September 2022). We first describe the upper-ocean thermal and dynamical structures of the Beaufort Sea during the transitional period from summer sea ice retreat to autumn sea ice advance. The cumulative air-sea net heat flux reaches its maximum at the autumn equinox in all four of these data sets. This is in part owing to the gradual reduction of shortwave radiation, and in part on account of more intense upward longwave radiation and turbulent heat flux released from the sea surface (the ratio of longwave, latent and sensible contributions is about 1:1:1). We show that both air-sea temperature and humidity differences play a crucial role in shaping the net fluxes, while the wind speed is not as important as these thermal factors. Furthermore, the temporal variation of ocean surface density during this transitional period depends on salinity rather than temperature, which influences water mass transformation in the Beaufort Sea.